The invention relates to an injection molding nozzle having a nozzle body with a flow passage with a nozzle opening and a mounting sleeve for a temperature sensor.
Such an injection molding nozzle, also called a “hot channel nozzle”, is well-known in the art and has been manufactured and sold by the Applicant for some time.
In the known injection molding nozzle, a temperature sensor which is provided for measuring the nozzle temperature in the area of the nozzle opening, is inserted into a cavity extending in the area of the nozzle opening into the interior of the nozzle body.
The temperature sensor is generally arranged in a small tube through which also the connecting wires for the temperature sensor extend. Since a heating coil extends around the nozzle body, the temperature sensor or, respectively, the tube in which the temperature sensor is disposed and through which the connecting wires extend must not project from the nozzle body. Therefore, starting at the cavity, the nozzle body is provided with an axially extending groove in which the tube including the wires leading to the temperature sensor are accommodated.
Since the cavity extends into the interior of the nozzle body but the groove extends in axial direction of the nozzle body, the front end of the tube with the temperature sensor needs to be bent over. Since the temperature sensor should be in good contact with the nozzle body to provide for a good heat exchange therebetween, the bending angle and bending procedure must be very precise which requires an expensive procedure.
Furthermore, an unevenness of the heating coil disadvantageously affects the force with which the temperature sensor is biased in contact with the bottom wall of the cavity. Also, this force is not always the same which result in different heat transfer resistances between the temperature sensor and the nozzle body in different injection molding nozzles.
Different heat transfer resistances between the temperature sensors and the nozzle bodies result in measuring inaccuracies which is disadvantageous since, as a result, the temperature of a nozzle body as measured by the temperature sensor in areas of the nozzle opening does not provide the same value for every nozzle. This is particularly disadvantageous if an injection mold includes several injection nozzles since different temperatures result in different viscosities of the plastic material being injected. This results in a different constitution of different areas of the product being manufactured and consequently in a loss in a quality of the product.
It is the object of the present invention to provide an injection molding nozzle with a temperature sensor arranged in the area of the nozzle opening wherein the temperature sensor is disposed reliably in good heat transfer contact with the nozzle body in a simple manner.